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[Reprinted fiom Journal of Economic Entomology, Vol. 14, No. 2, April 1921 



SOME PROBLEMS IN GREENHOUSE INSPECTION WORK 

IN INDIANA 

Bv Harry F.Dietz, Department of Conservation, Indianapolis^ 

The total value of the greenhouses of the United States is between 
$75,000,000 and $100,000,000. In Indiana alone there are 4,500,000 
square feet of ground covered by greenhouses conservatilvey valued at 
$5,000,000. Our State ranks seventh among the commercial flower- 
growing states of the Union_, being surpassed only by New York, 
Pennsylvania, New Jersey, Illinois, Massachusetts, and Ohio. Little 
thorough work relating to the life history and control of the most com- 
mon and destructive of these insect pests or plant diseases has been 
done. The florists have been left largely to shift for themselves and to 
devise control methods good, bad, and indift'erent. Generally only in 
cases where the destruction of an entire crop has been threatened, 
through the spread of a serious pest such as the chrysanthemum midge, 
have entomologists as a whole aided the florists. 

The problems arising in the inspection and certification of greenhouse 
plants for intra and inter state shipment have not been given the careful 
and thorough consideration they deserve. The writer does not presume 
to say how these problems should be dealt with, but will point out and 
illustrate by specific cases, the problems that have arisen in Indiana in 
order to awaken an interest in the matter. 

^Published with the permission of the Director of the Department of Conservation 
and the Chief of the Division of Entomology,^^ 



April, '21] DiETz: greenhouse inspection 189 

It is necessary here to point out that there is a very important dif- 
ference between greenhouse grown plants and nursery stock at the time 
each is distributed. Nursery stock is dormant when shipped. The 
leaves are off and practically all soil is removed from the roots. There 
are some exceptions as in the case of conifers and other evergreen plants. 
On the other hand plants grown under glass are generally shipped in a 
growing condition. Except in the case of cuttings and bud-wood, 
defoliation is out of the question and so is the removal of soil from the 
roots. Therefore, any insect or disease attacking the leaves, stems, or 
roots, are generally carried with the plants. 

The first problem is, "What shall we regard as 'clean' plants?" — in 
other words, "What are plants free from dangerously injurious insects 
and plant diseases?" The following list of greenhouse insects (including 
mites) and plant diseases has been arranged in accordance with the 
prevalence of the pests in Indiana greenhouses (See p. igo). 

It is evident that many of the tropical and sub-tropical insects, such 
as the mealy-bugs and scale insects listed, are serious pests in California 
and Florida and along the Gulf of A-Iexico ; therefore, their very presence 
in a greenhouse ought to be sufficient grounds for refusing the grower a 
permit to ship plants to the regions mentioned. The terminal inspec- 
tion systems in use in California and Florida will prevent infested stock 
from entering these states. Yet, should the presence of these pests 
warrant the refusal of a permit to ship when the plants are grown for 
northern distribution only, and where perhaps the only persons who will 
have trouble with them will be florists and their patrons ? This distribu- 
tion of, in most cases lightly infested, plants from florist to florist and 
from florist to patron has lead to some interesting results. Ten years 
ago the coleus was one of the most popular bedding plants in Indiana, 
But today that popularity has decreased so far that few florists grow 
this plant, and all this is due to mealy-bugs. The florists could not, 
or did not, keep these plants free from the pest with the result that when 
the plants were bedded out with others during the summer it was only 
a matter of time until the other plants, as well as the coleus, were infested 
and the bed ruined. The patrons of the florist have learned that the 
coleus is a plant not to buy because of the danger of their being infested 
with mealy-bugs. 

Many Indiana florists have also discontinued the growing of palms 
and other subtropical plants used for decorative purposes because of the 
difficulty they have had in controlling the tropical and subtropical scale 
insects attacking them. Ten years ago a greenhouse was incomplete 
without a stock of palms and other tropical decorative plants. Such 
plants usually went from bad to worse year by year and as they died 



LIBRARY OF CONGRESS 
.*. DECEIVED 

MAT 9 1923 

DOCUMENTS DIVISION 



190 ^^^ JOURNAL OF ECONOMIC ENTOMOLOGY 

INSECT PESTS INCLUDING MITES 



[Vol. 14 



Pest 



Red Spider (Tetranychits telarius Linn.)' 



Mealy Bugs {Pseudococcus cilri Risso and P. 
adonidum Linn.)'' 



Coleus, geraniums, palms, rubber plants, Boston 
and related ferns, dracenas. etc. 



Greenhouse White Fly {Trialeurcdes vaporarioriim 

Westw )2 



Greenhouse Thrips (Heliothrips haemorrhoidalii 
Bouche')2 



Plant Lice 



Boston Fern Scale {U emichionaspis aspidislrae 
Sign.)2 



Chrysanthemum Midge {Diarlhronomvia hypogaea 
F. Lw.)2? 



Greenhouse Leaf-tier {Phlyclaenia jei-rugalis 
Hubn.)i 



Rose Midge (Dasyneura [Neocerata] rhodophaga 
Coq.)2? 



Rose or Oblique-banded Leaf-roller {Archips 
[Cacoecia] rosaceana Harr.)i 



Florida Fern Worm {Eriopiis [Callopislria] floriden- 
sis Guen.)2 



Soft Scale {Coccus hesperidum Linn.)- 



Hemispherical Scale {Saissetia hemisphaerica 
Targ.)2 



Oleander Scale (Aspidiotus hederae Vall.)^ 



Florida Red Scale {Chrysomphalus aonidum 
Linn.)- 



Boisduval's scale (Diaspis hoisduvalii Sign.)^ 



Strawberry Root-worm {Paria canella Fabricius 
vars. aterrima Oliv. and quadriguttalus Lee.) 



Cyclamen Mite {Tarsonemus pallidus Banks)''? 



Host on which it may be distributed 



Roses, carnations, chrysanthemums, smilax, palms, 
aspidistra, etc. 



Pelaigonium, fuchsia, primulas, celestial peppers 
and ornamental solanums. 



Rose, carnation, chrysanthemum, troton, aspidis- 
tra, Ficus spp. a zalea, etc. 

Aphis rufomacidala Wilson and Macrosiphum 
sanbcrni Gill, on chrysanthemums'; Macrosi- 
phum rosae Linnaeus on rose' ; Myzus persicae 
Sulzer on carnations'; A.phis aossypii Glover on 
begonias, Easter lilies^?, Cetataphis lataniae 
Bdv. on Kentia palms. ^ 



On Boston and other ferns, aspidistra. 



Species and varieties of the genus Chrysanthemum 



Chrysanthemum, cineraria, primulas, carnation, 
rose. , 



Roses. 



Rose, carnation 



Various genera, species and varieties of greenhouse 
ferns. 



Ferns, palms, crotons, ornamental citrus plants, 

camellia, Ficus spp.. bay trees, orchids, etc. 
Same as Soft Scale. 



Palms, cycads, ornamental citrus plants, orchids, 
bay trees. Olea fragrans. etc. 



Palms, Ficus spp., ornamental citrus plants, 
Pandanus veilchii, Dracena indivisa. aspidistra, 
cypripediums. 



Palms, orchids (Cattleya spp.). 



Roses? Soil (larvae). 



Geranium, 
dragons. 



Chaff Scale {Parlatoria proteus Curt.)^ 



The Crazy Ant {Prenolepis longicornis Latr. )" 



cyclamen, chrysanthemums, snap- 



O rnamental citrus plants, orchids (Vanda spp.). 
In peat around orchids (Cattleya spp. and Vanda 
spp.) Only one record fro m Indiana. 



The Greenhouse Orthezia (Orthezia insignis 
Dougl.)2 



The Argentine Ant (Iridcmyrmex humilis Mayr)^ 



Disease 



Root and Stem Rot (Rhizoclonia sp.) 



Wilt, Stem Rot or Die Back (Fusarium sp.) 



Carnation Rust {Uromyces caryophillinus iSchrank] 
Winter) 



Bud rot iSporotrichum poae Peck) 



Wilt (Fusarium sp.) 



Anthracnose (Cloeosporium rosae Halsted) 



Cane Blight (Coniothyrium fuckelii Saccardo) 



Crown Gall* (Bacterium Itimefaciens Erw. Smith 
and Townsend) 



Rust (Puccinia anthirrini Dietel and Holway) 



Coleus. Only one record from Indiana greenhouses, 
other hosts are lantana, verbena, chrysanthe- 
mum, gardenia. 



Pandanus, dracena, dieffenbachia, and aspidistra 
See text p. 193 for a discussion of this insect. 
Has not been found in Indiana. 



Host on which it may be distributed 



Carnation. 



Carnation. 



Carnation. 



Carnation. 



Chrysanthemum. 



Rose. 



Rose. 



Snapdragon. 



'Holartic insects 



-Tropical or semitropical insects. 



April, '21] DiETz: greenhouse inspection 191 

were replaced by others. Infested plants served as a harbor for scale 
insects and a source from which plants like ferns, which v^^ere often grown 
in the same house, became infested. When a florist sold a palm or 
similar plant he often got it back during the winter as a "boarder." 
Often he took it back in spite of his better judgment and set it among 
his own plants which he had fought hard to keep clean. In view of these 
facts should the grower who takes in "boarders," which are generally 
scale infested, be allowed to ship plants to another grower in another 
state who does the same thing? Or, if not, to what treatment should 
lightly infested plants be subjected to kill any infestation of scales or 
other insects occurring on them? 

Ferns are delicate plants and when they become infested with insects 
it is practically impossible to "clean them up" without injuring the 
plants. Hence, what disposition should an inspector make in the case 
of ferns that show a very slight and scattered infestation of any of such 
scale insects as the soft scale, the hemispherical scale, or the Boston 
fern scale? It is needless to point out that a grower of ferns free from 
these insects is always afraid of introducing these pests on plants he 
buys. One florist in a small Indiana city bought several thousand 
fern plants infested with soft scale from a large grower and distributor 
in another state. These he unwittingly set among his clean stock with 
rather disastrous results. How can occurrences like this be best pre- 
vented ? 

The rapid spread of the chrysanthemum midge shows what may 
happen when a serious greenhouse pest becomes established in the 
greenhouses of one or more large growers. In 1914 it was known only 
from the houses of one large chrysanthemimi grower, but by 1917 eight 
of the large distributors in widely separated parts of the United vStates 
had serious infestations. Fortunately we know now how to control 
the insect and most of the larger growers in Indiana have it under abso- 
lute control and several have practically exterminated the pest in their 
greenhouses. Nevertheless, its spread is continuing. In 1916 when 
widespread warnings were disseminated many of the smaller growers, 
such as local florists, became frightened and refused to buy mum plants 
for two or three years. But during the spring of 1919 and 1920, lead 
on by the high price of cut flowers, many florists "plunged" heavily on 
mums. Even those who bought only such plants as they needed of 
some new and popular variety often got the midge with them. One 
large distributor got an infestation in this manner. He fortunately 
did not buy any chrysanthemum plants from 1914 to 1919 and as a 
result had no midge. In 1919 he bought 200 plants of a new variety 
and luckily escaped the pest. But in 1920 he bought 250 plants of a 



192 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 

new variety from a jobber and with them came a light infestation so 
that this fall not only the plants he bought but two of his own varieties 
were infested slightly. 

In many respects the rose midge is like the chrysanthemum midge. 
Though this insect has been known in the United vStates since 1887, its 
outbreaks have been more or less sporadic and probably dependent on 
the distribution of new varieties which have served as favorite food 
plants. The last distribution and resulting outbreaks of this pest took 
place with the dissemination of the popular rose, Ophelia. There is 
little doubt but that the plants, sent out by one of the several distribu- 
tors of this variety, were infested with this midge. Ophelia is a fine 
seed parent and also shows a tendency to "sport" easily. Many of its 
"sports" and seedling offspring are held in high esteem by the florists 
and are constantly gaining in popularit}^ with the flower-buying public. 
The reason I have mentioned this fact is that Indiana observations 
indicate that some of these sports and seedlings show the same susceptiljil- 
ity to the attacks of rose midge that their parent does and there are 
indications that another outbreak of this insect over w4de areas is going 
to result. 

The greenhouse white fly, because of the range of host plants it attacks, 
is very troublesome. It is difficult to control, especially when hydro- 
cyanic acid gas is not used. Florists who have not had experience with 
this insect often scoff at the idea that it is a serious pest. But many 
Indiana florists have changed their minds regarding its importance. 
Those who have attempted to grow semi-hardy perennials like buddleia 
and bouvardia under glass or those who have lost a crop of indoor asters 
through its attack do not think it a pest of secondary importance. 
Those who grow fuschias, salvias, primulas and celestial peppers know 
that it is no easy task to control white fly. Yet one can find growers 
of some of its favorite food plants who have little or no difficulty in hold- 
ing the insects in check, often without resorting to cyanide fumigation. 
In view of these facts what disposition should an inspector make of 
plants lightly infested with white fly ? 

Those insects and mites that occur out-of :doors in the northern two- 
thirds of the United States but have invaded greenhouses, like the red 
spider, the greenhouse leaf-tier, the rose leaf-roller, and the strawberry 
root-worm, present an interesting case. The first and the last named 
become serious pests out-of-doors but the other two do not seem to be 
nearly as serious pests in the open as under glass. If Indiana experiences 
are to be taken as a basis, it is safe to assume that both the leaf-tier 
and leaf -roller have been far more widely distributed through the medium 
of infested hosts than through the invasion of the greenhouses by moths. 



April, '21] DiETz: greenhouse inspection 193 

or caterpillars, in widely separated localities. We have noticed that 
when any large grower and distributor has an outbreak of these two 
pests it is not long before a number of the smaller growers who have 
bought from the infested source have an outbreak. Hence, shall the 
presence in a greenhouse of any of these insects mentioned, even though 
they are being held in check successfully, warrant the withholding of a 
certificate of inspection? 

The tropical ants are pests that seem to be gaining a foothold in our 
northern greenhouses. One of our florists bought a large collection of 
orchids from a jobber. With these he got the following insect pests, — 
a hea\'y infestation of Parlatoria ■pergandii Comst. on vandas, a heavy 
infestation of Diaspis boisduvalii Sign, on cattleyas and a scattering 
infestation of Coccus pseudohesperidum Ckll. and Targionia hijormis 
Ckll. (both new coccid records for Indiana) on the same host. But 
what is probably more important than all these scale insects, he got a 
heavy infestation of the crazy ant — Prenolepis longicornis Latr. with 
nests in the peat in which the orchids were growing. Just what the 
outcomie of its introduction into this Indiana greenhouse will be, remains 
to be seen. What action should the state in which this shipment 
originated have taken? And what action should the State of Indiana 
take to prevent the further distribution of this insect? 

It is a common thing for Indiana florists to buy plants like aspidistra, 
ficus, Dracena indivisa and Pandanus veitchii that have been grown out- 
of-doors (or with slight protection in the winter) in the southern states. 
I was amazed to find that the greenhouses where a large southern 
distributor of aspidistras grew these plants were alive with the Argentine 
ant. What action should be taken to prevent the spread of this insect, 
northward ? 

Though comparatively little is known about greenhouse insects, 
far less is known about most of the diseases attacking plants grown under 
glass. There is carnation rust, the Fusarium root rot, and the Rhizoc- 
tonia branch and stem rot on this host. There is the snapdragon rust 
which has spread over the whole United States in the past twenty years. 
The widespread distribution of this disease might at one time have been 
checked. On roses we have such diseases as anthracnose and cane 
blight. There are doubtless many others which will attract attention 
following intensive study. Should the presence of any of the diseases 
mentioned in a greenhouse warrant the withholding of a certificate of 
inspection? Can infected plants be sent under a qualified certificate of 
inspection? Are these diseases dangerously injurious? 

At present, three alternatives are open to state inspectors relative to 
plants grown under glass. The first is to let any and all persons who 



194 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. I4 

desire to ship greenhouse plants do so on the grounds that such plants 
do not come under the regular nursery inspection requirements. Technic- 
ally this view is correct. The second alternative is to inspect the plants 
and issue a certificate if the plants are free from insect pests and plant 
diseases at the time of inspection and if measures are being taken by the 
grower to keep them so. The third alternative is to issue qualified 
certificates of inspection provided there are no dangerously injurious 
insects or diseases present or new and uncommon ones which are very 
restricted in their distribution. Certain combinations of these three 
alternatives are in use in some states. In these cases if a grower is refused 
a certificate of inspection he can ship his plants by merely attaching a 
statement to them that they are greenhouse grown and are thus exempt 
from inspection. Thus the man who grows clean stock for distribution 
is at a disadvantage in that he must compete with the one who does not. 
Also in such cases anyone who wants to sell greenhouse plants, no matter 
how badly they are infested with insects or infected with diseases, can 
sell them and there is nothing in most states that will protect the buyer 
of these plants except the contract he has with the man from whom he is 
buying. 

Now if the certification of greenhouse plants is undertaken what shall 
the basis of such certification be ? How often and when shall the plants 
be inspected? Thirty days will often change the entire aspect of the 
insect and disease conditions in greenhouses. If there is but a single 
inspection when shall that be ? The presence of the rose midge may not 
even be suspected if an inspection is made from December to March. 
Chr\^santhemiun midge, especially where a light infestation occurs, 
might be overlooked if the inspection were made during the summer, 
from the last of June to the first of October. During the months from 
December to April only the most careful inspection would reveal the 
occurrence of the strawberr}^ root-worm. 

In general, it might be said that two inspections, one in the summer 
and one in the winter, ought to give the inspector a good idea not only 
of the insect and disease conditions in a given greenhouse but also an 
idea of the grower's ability to "clean up" his plants and keep them so. 



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